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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9474f51fa175af16c8a881104578596b41008ac038b1f1ec59571b1728d4d421' 
  AND token = '3xfbMFlwC+S05SM54ud31Dwfs+zpz72H84mYsY0FE0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}